1. Field of the Invention
The invention relates to railroads generally, and more particularly to signal compliance train control methods and systems.
2. Discussion of the Background
Many methods for controlling trains are known. Such methods include the Automated Block Signaling (ABS) and Centralized Train Control (CTC) methods. In such methods, train tracks are divided into sections, referred to in the art as blocks, and an operator is relied upon to move a train in compliance with wayside signals that are positioned some distance before a block boundary. In traditional ABS and CTC systems and the like, the wayside signals comprise colored lights that are visually observed by the operator. In more modern variants of these systems, sometimes generically referred to as communication-based train control (CBTC) systems, the signal information is transmitted into the cab of a locomotive. Examples of such systems include cab signaling systems and the TRAIN SENTINEL™ system available from the assignee of the present application, Quantum Engineering, Inc. Some of these systems, including the TRAIN SENTINEL™ system, ensure operator compliance with signal information transmitted into the cab.
Such block-oriented systems vary in their implementation. However, one aspect shared by several of these systems is that a restrictive signal in one block may be caused by conditions in the next block. A problem shared by such known systems is that there is no provision for lifting the restrictive signal in a block if conditions in the next block causing the restrictive signal “clear up.” Causing a train to operate under a restrictive signal unnecessarily makes operation of the train less efficient, which increases costs.
What is needed is a method and apparatus that allows the lifting of a restrictive signal after a block has been entered when such restrictive signal is no longer necessary, and that allows a less restrictive signal to be recognized even after a train has passed the aforementioned wayside signal device.